Web printers are used for very high volume print runs, say greater 1000 copies but could well be more than 1 million copies for newspapers and the like. Traditionally, web printers use offset printing where plates embossed with the images and/or text are mounted on large drums that roll over the web to transfer the ink. Producing the plates and aligning the various drums for registration of each color, and for correct registration of the print of both sides of the web, is exceptionally time consuming—usually several hours. However, once set up, the web is printed at very high speeds. These are typically in the range of 3 meters per second up to 6 meters per second.
In light of the set up time, web printing becomes more efficient and cost effective as the size of the print run increases. For short print runs—say less than 1000 copies—web printing becomes uneconomical.
To address this, web printers with inkjet printheads have been developed. The Hewlett Packard Inkjet Web Press is a thermal drop-on-demand inkjet production color printer capable of speeds of 400 linear feet per minute (approx. 2 meters per second) on webs as wide as 30 inches (0.762 m). CMYK pagewidth (or web width) printheads are duplexed to print both side of the web at an addressable 1200×600 dpi resolution. The printer price is approximately US$2.5 million and the consumable cost is about two cents for a four-color letter/A4-sized image at 30% coverage.
The inkjet web press is a digital printing process and hence there are no printing plates. This reduces the time and cost of the print run but the alignment of the printing from the printheads needs to be precise and this process remains relatively time consuming. The leading edge of the web is manually fed through the press from the media roll unwinder at the input to the roll winder at the outlet by experienced technicians. The press has five main components—a print cabinet, a drying cabinet, a paper turner and aligner, a second print cabinet (for the other side of the web) and another dryer. The overall size of the press is less than a traditional offset press but still the footprint exceeds 35 m2.